Insulator.



J. D. E. DUNCAN, DEGD.

L. E. H. DUNCAN, EXEGUTRIX.

INSULATOR.

APPLICATION FILED JAN.2, 190s.

Patented Feb. 16, 1915.

llll uuum UNITED STATES PATENT OFFICE.

E. DUNCAN, OFEAST ORANGE, NEW JERSEY; LENA ELIZABETH HILL DU NCAN- EXECUTRIX OF SAID JOHN D. E. DUNCAN, DECEASED.

INSULATOR.

Specification of Letters Patent.

Continuation in part of application Serial No. 391,893, filed September 9, 1907.

SerialNo. 408,882.

T0 at! whom it may concern:

Be it known that 1, JOHN D. E. Duncan, a citizen of the United States, now residing at East Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements Relating to Insulators, of which the following is a specification, taken in connection with the accompanying drawing, which showsanallustrative embodiment of the invention 1n elevation, parts being indicated in section.

This application comprises sub ect-matter disclosed in my copending patent application 391,893, filed September 9-, i907, which matured on February 25, 1908 into Patent 880,203 of which this application is a continuation in part.

This invention relates to insulators and relates especially to high potential insulators such as are adapted for use on power transmission lines where a number of compound insulators may be used in ser es and so connected together as to be sufiiciently rigid to resist torsion and compression strains as well as tension. Each insulator of the series may be composed of a number of nested portions or domes having attached petticoats, the thickness of the inner nested portions being made less than that of the outer ones to properly reduce the potential on the opposite faces of the inner elements due to condenser action and the var ous ele ments and compound insula ors being selfprotecting so that even under extreme conditions excessive potential will cause flash ng or arcing around them-instead of causing puncture or injury by excessive surface leaka e.

In the illustrative embodiment of this invention shown in the drawing, each compound insulator may comprise an nner dome 79 having a substantially uniform thickness and provided with the integral depending petticoat 92. If desired for particularly high voltage service the inner petticoat and dome may be made of some material having higher specific resistance than the outer domes, especially high resistance material suitable for the inner dome being for example glass, micanite or other highly insulating compound which may be molded directly upon the connector end. Thls inner element of the compound insulator may be nested within one or more other insulating Patented Feb. 16,1915.

This application filed January elements comprising domes and integral pettlcoats formed of porcelain or other insulating material and these elements may be so arranged as to be readily assembled by nesting them together, that is, by simply slipping the domes inside of one another, the various elements being preferably so formed as to allow this method of assembly. As indicated, the intermediate dome 78' may have a substantially uniform thickness and be provided with the depending intermediate petticoat 82 which may be slightly thinner adjacent its edge. The outer dome 85 of substantially uniform thickness may have the integral outer petticoat 72 of gradually decreasing thickness toward its edge and these outer elements may be formed of porcelain as is also the case with the inner insulating element for some service.

The series of nested domes may be supported within a suitable body portion or head 73 which may be provided with a suitable inclined supporting shoulder 83 adja cent its lower edge. The outer dome may be formed with a cooperating shoulder or series of projections 89 and may also be provided on its inner face with the shoulder 86 with which the shoulder 87 on the intermediate dome cooperates, this intermediate dome having, if desired, a suitable inclined shoulder 95 on its inner face. The inner dome may have similar projections or inclined shoulders 96, 97, the latter cooperating with the inclined or flaring portion 98 on the connector 71. The insulating elements having been first separately tested, if desired by subjecting them to potentials greater than required to flash or are around the petticoats under service conditions, may be assembled by nesting them together, that is, by slipping them one within another within the head or body portion 7 3 and arranging the connector 71 properly within the inner dome. These parts may then be locked or rigidly secured together in proper position by the use of cement, (which may be made waterproof by treatment with shellac, paraflin, etc.) pressure members or other suitable binding means insulators may be mounted in the series in any desired way by securing together the metallic members thereof, that is, the heads and connectors, for example by screwing or otherwise securing the lower end of the connector 71 into the head 66 of the insulator below. The metallic portion of the insulator at one end of the series may be supported in any desired way and the other terminal metallic member may be secured to a wire or other conductor by any suitable means. As indicated in the .drawing, the connector 64 of the lower insulator may be mounted in a suitable support 62 so as to be rigidly supported from the base 61 while the conductor 81 may be secured to the head 73 of the top insulator as by the use of the yoke 80 bolted down upon it.

Under normal dry weather conditions, the cement or other binding means locking the elements of the compound insulator together acts somewhat as the conducting element of a condenser, so that each nested dome of the insulator between the layers of cement, etc., is probably subjected to about the same proportion of the total potential on the compound insulator as is determlned by the constants of these different condensers acting in series. Considering, for simplicity a twopart compound insulator in which the domes are of the same material and thickness the inner dome because of its relatively smaller surface in contact with the cement so as to have condenser action has a considerably less capacity as a condenser as compared to the outer dome. Since in a series condenser alte'rnatingv circuit the potential across each condenser is inversely proportional to its capacity, the inner dome having a smaller capacity is for generally simllar reasons thus subjected to a greater potential which cannot be so well taken care of and may lead to 1ts plmcture or failure. The capacity of the inner dome as a condenser may, however, be increased by making thinner the porcelain or other insulating dielectric of thls insulator dome which apparently seems to increase the capacity and thus relieve the working potential on this dome to a greater extent than the insulating action of the dome is reduced by its decreased thickness. Or, to put the matter'in a little different way, the inner dome may with advantage be made of such thickness and proportions as to safely withstand the normal potential to which it is subjected by this condenser action and the outer dome or domes in which it is nested are made proportionately thicker so as to insure against the inner dome being subjected to an excessive proportion of the total potential on the insulator because of the condenser efi'ects re-' ferred to. By making the inner dome of some such compound insulator as is illustrated in the drawing of considerably less thickness the potential thus exerted upon its opposite faces that is, the condenser potential, is materially reduced and a much more desirable distribution of condenser potential on the various domes is secured if the inner ones are made considerably thinner than those outside them; in some cases it may be desirable to make the nested domes of a uniform thickness substantially proportional to their mean diameter. By making the inner The length of the inner petticoats is made I considerably less than the length of the outer ones so as to limit the potential that can be maintained on the opposite faces of the dome byallowing leakage over the sur-- faced the petticoat. The inner petticoat 92, for instance, must, in order to properly limit the potential on the inner dome, be made very much shorter than the intermediate petticoat because having a less width of leakage path. Under wet weather conditions the outer surface of the outer petticoat of the compound' insulator becomes wet and also under some conditions considerable condensation moisture collects on the other parts of the petticoats so as to materially decrease the resistance to surface leakage. The petticoats may be made sufficiently flaring so that the angle between the cotiperating faces of adjacent petticoats is such that the striking or arcing potential between two opposite points on adjacent petticoats is less than-is required to leak along the surface between these two points, so

that undue surface leakage andheating of the parts is thereby prevented. The several compound insulators" may be so mounted that the striking or arcing po tential between the edge of the outer petticoat 72 and the head 66 of the insulator below is less than is required to leak along the surfaces of the various petticoats interposed between. The distance over the various petticoats comprising each insulator is thus made suificiently great so that undesirable surface leakage will not take place at any potential that can be maintained before direct'arcing from the edge of the out.erpetticoat to the next compound insulator below takes place. This direct arcing which acts to relieve the potential and prevent undesirable surface leakage may be romoted if desired by the interposition 0 suitable arcing members which may be supported on the petticoats or preferably on portions'of the compound insulators. As indicated, the arcing member 68 may be removably mounted" on the head 66 by slipping the spring clip on this arcing member into the groove 67 parts of this arcing member held together by 't'h'e rivets 69 securely, holding the ,mem-

said insulators comprising a body thickness than her in position. Suitable-tips'ZO and'91are formed on this arcing member, preferablyconsiderably outside of the Petticoats and in position to coiiperate with the similar tip 93 on the arcing member 76 which may be similarly mounted in a groove 75 in the head 73. If desired anotherarcing member 63 may be mounted on the support 62 and have a tip 90, these tips or arcing portions of the arcing members being as indicated preferably located considerably outside of the line of the petticoats, that is, farther away from the axis of the insulators so as to draw and keep away from the petticoats any are that may be formed.

- Under extreme service conditions, varying condensation or collection of dust on the insulators may cause a very excessive voltage to be thrown on one or more petticoats or compound insulators. For this reason, it is highly important to have the various insulators and their component insulating elements self-protecting so that even under these extreme conditions the excessive potential will cause flashing or arcing around them instead of either puncturing or injuring them by excess surface leakage. Each of the petticoats may be made sufiiciently short and the compound insulators may be placed close enough together to make them self-protecting and to allow such arcing to take place without damage and in suflicient amount to substantially equalize the potential carried by the various compound insulators and their elements. Such arcing naturally tends to quickly dry off the surface of the insulator or burn off dustcollected upon it so as to bring up the impaired resistance of any element and restore the normal distribution of potential throughout the system.

Having described this invention in connection with illustrative materials, proportions and embodiments, to the details of which disclosure the invention'is not, of course, to be limited, what is claimed as new and what is desired to be secured by Letters Patent is set forth in the appended claims.

1. In insulators, a plurality of compound insulators, connectors substantially rigidly securing said insulators together, each of portion, more than two nested domes within said body portion and provided with integral flaring petticoats, said inner domes having shoulders cooperating with enlarged portions on said connectors, binding material locking the parts of said compound insulators together, each of said domes being of substantially uniform thickness and the inner domes being of considerably less the outer domes to reduce the shorter g, p the potential on said inner domes andpro potential on said inner domes, petticoats being considerably than said outer petticoats'to liinit condenser said inner mote the self-protecting action of theiiiSulating elements, arcing members .moiinted on said insulators and having tips extending out beyond the line of said petticoats to allow arcing away from said petticoats and promote the self-protecting action of said compound'insulators.

2. In insulators, a plurality of compound insulators mounted in series, each of said insulatorscomprising a body portion, a se ries of nested domes within said body portion and provided with integral petticoats, binding means holding the parts of said compound insulators together, each of said domes being of substantially uniform thick nessand the inner domes being of "considerably less thickness than the outer domesto reduce the "condenser potential on saidinner domes, said inner petticoats being considerably'shorter than the outer petticoats to promote the self-protecting action of the insulating elements, said inner domes being formed of more highly resistant material than said outer domes, and means to allow direct arcing around one of said compound insulators and away from the petticoats thereof to promote the self-protecting action of said insulator.

3. In insulators, a plurality of compound insulators mounted in series, each of said insulators comprising a body portion, a series of petticoats and integral domes arranged one within another and held in position and arcing members attached to said insulators to allow direct arcing between them away from the petticoats of said insulators to promote the self-protecting action of said insulators.

4. In insulators, a plurality of insulators mounted in series and arcing members mounted on the heads of said insulators to allow arcing around said insulators out of substantial contact therewith to minimize arcing damage and thereby promote the self-protecting action of said insulators.

5. In insulators, a series of more than two petticoats having integral domes arranged within one another, binding means to hold the parts of said insulator together, each of said domes being of substantially uniform thickness, said insulator comprising an inner dome of considerably less thickness and formed of more highly resistant material than an outer dome and an inner petticoat considerably shorter than an outer petticoat to promote the self-protecting action of the insulating elements.

6. The compound insulator comprising a body portion, a series of petticoats having integral domes arranged one inside another in said body portion, and protected and substantially inclosed thereby, binding means to hold the parts of said insulator together, said insulator comprising an inner dome of considerably less thickness than an outer dome to limit thecondenser potential on said inner dome, and an inner petticoat of considerably less length than an outer petticoat to promote the self-protecting action of the insulating elements.

7. The compound insulator comprising a series of pctticoats and connected supporting domes arranged one inside another and means to hold the insulating elements in position, one of said inner domes being of substantially less thickness and formed of more highly resistant material than an outer dome.

8. The compound insulator comprising a plurality of insulating petticoats and attached imperforate insulatin domes each of substantially uniform thic essand arranged one inside another and means to secure the insulating elements in position, the innermost of said insulating elements having a dome of considerably less thickness and having an attached petticoat of considerably less length and resultant surface leakage resistance than the adjacent outer insulating element to limit the condenser potential on said innermost dome and promote the selfprotecting action of said insulating elements.

9. The compound insulator comprising a plurality of etticoats and attached domes arranged one inside another and means to hold the insulating elements in position, one of said inner domes being formed of more highly resistant material than one of said outer domes. v

10. The compound insulator comprising a plurality of insulating petticoats and attached imperforate insulating domes arranged one inside another and means tosecure the insulating elements in position, the innermost of said insulating elements having a dome of considerably less thickness and having an attached petticoat of considerably less length and resultant surface leakage resistance than the adjacent outer insulating element to limit the condenser potential on said innermost dome and promote the self-protecting action of said insulating elements.

11. The compound insulator comprising a plurality. of insulating elements arranged one inside another, one of said inner insulating elements being considerably thinner and being formed of more highly resistant material than one of said outer elements.

12. An insulator comprising a plurality of nested domes provided with integral flaring petticoats and with a head within which said domes are mounted and an arcing member having a spring clip detachably mounting said arcing member on said head and having tips located beyond the line of said petticoats and extending toward the same.

13. An insulator comprising a petticoat and an arcing member mounted on said inranged one inside another in said body portion, each of said inner domes being of less thickness than the dome within which it is located to limit the condenser potential on said inner domes.

15. The compound insulator comprising a body portion and a series of more than two petticoats and attached imperforate domes arranged one inside another in said body portion, and binding means to hold the parts ofsaid insulator in position, each of said domes being of less thickness than the dome within which it is located, and each of said petticoats ofi'ering less resistance to the passage of electricityaround it than the petticoat within which it is located.

16. The compound insulator comprising a series of more than two petticoats and connected imperforate domes arranged one inside another, each of said inner petticoats having less resistance to the passage of electricity around it than the petticoat within which it is located.

17 The compound insulator comprising a bodypo'rtion, a series of imperforate-domes and integral petticoats nested within said body portion, binding means to hold the parts of'said insulator in position, each of said domes being of less thickness than the dome ,within which it is located to reduce the condenser potential on said inner dome and each of said pettieoats being considerably shorter and offering less resistance to the passageof electricity around it than the petticoat within which it is located to promote the self-protecting action of the insulating elements.

18. The compound insulator comprising a body portion, a series of imperforate domes nested within said body. portion and provided with integral petticoats, binding means holding the partsof said compound insulator together, each of said domes being of substantially uniform thickness and each inner dome being of considerably less thickness than the dome outside thereof to reduce the condenser potential on said inner dome and the inner petticoat integral with said inner dome being considerably shorter than the petticoat outside thereof to promote the self-protecting action of the insulating elements. n

19. In insulators, a plurality of compound insulators, connectors substantially rigidly securing. said insulators together, each of said inner petticoats being considerably.-

shorter "than'said outer petticoats to limit the potential on said inner domes and promote the self-protecting action of the, insulating elements.

20. In insulators, a plurality of compound insulators mounted in series, each of said insulators comprising a body portion, a series of imperforate domes nested Within said body portion and provided with integral petticoats, binding means holding the parts of said compound insulators together, each of said domes being of substantially uniform thickness and the inner domes being of considerably less thickness than the outer domes to reduce the condenser potential on said inner domes, and said inner petticoats being considerably shorter than the outer petticoats to promote the self-protecting action of the insulating elements.

21. The compound insulator comprising a metallic body portion, a series of petticoats having integral domes arranged one inside another Within said body portion and protected and substantially inclosed thereby, binding means rigidly holding the parts of said insulator together, said insulator comprising an inner dome of considerably less thickness than the outer domes, to limit the condenser potential on said inner dome and an inner petticoat of considerably less length than an outer petticoat to promote the self-protecting action of the insulating elements.

The compound insulator comprising a metallic body portion and a series of petticoats having attached imperforate domes arranged one inside another within said body portion and protected and substantially inclosed thereby, said insulator comprising an inner dome of considerably'less thickness than an outer dome to limit the condenser potential on said inner dome and an inner petticoat having less resistance to the passage of electricity around the same than one of said outer petticoats to permit the self-protecting action of the insulating elements.

23. A compound insulator comprising a metallic body portion, a series of petticoats having integral domes arranged one inside another within said body portion and protected and substantially inclosed thereby,

and binding-means to hold the parts of said insulator rigidly together,- one of said inner petticoats having considerably less resistance to the passage of electricity around the same than one ofsaid outer petticoats to permit the self-protecting action of the insulating elements.

24. The compound insulator comprising a metallic bodyportion, a series of more than two petticoats and attached imperforate domes arranged one'inside another within said' body portion and protected and substantially' inclosed thereby, each of said inner domes being of less thickness than the dome within which it is located to limit the condenser potential on said inner domes.

25. In insulators, a series of compound insulators provided with petticoats and attached nested imperforate domes and metallic body portions Within which said domes are supported and substantially inclosed and protected and connectors secured to said body portions and substantially rigidly securing said insulators together and holding them spaced apart in series and out of interfering distance and a support connected to the lower insulator to support said substantially rigid connected series of insulators.

26. In insulators, a plurality of insulators comprising metallic bodies and petticoats having connected imperforate domes located within said bodies, said bodies being provided with attaching grooves and arcing members having clips engaging said grooves to rigidly support said arcing members from said heads, said arcing members being provided with approaching tips extending out considerably beyond the line of said petticoats to keep any arcs formed away therefrom.

27. An insulator comprising a series of petticoats and attached imperforate domes, a metallic body Within which said domes are located, said body being provided with an annular groove and an arcing member having a spring clip engaging said groove and rigidly supporting said arcing member on said body, said arcing member being provided with a tip extending out considerably beyond the line of said petticoats.

28. In insulators, a series of insulators comprising metallic bodies, insulating members secured to said bodies and comprising petticoats and arcing members secured to said bodies and having cooperating t ps extending out considerably beyond the line of said petticoats.

29. An insulator comprising a metallic body provided with an attaching depression, an insulating member provided with a petticoat secured to said body and an arcing member having means cooperating wlth said attaching depression to disengageably and rigidly mount said arcing member upon ing a substantially uniform thickness substantially proportional" to its mean diameter to equably apportion the condenser potential on said domes and each of said petticoats ofi'ering less resistance to the passage of electricity around it than the petticoat within which it is located to promote the selfprote'cting action of the insulating elements.

31. The compound insulator comprising a metallic body portion, a series of more than two petticoats and integral imperforate I domes nested within said body portion" and protected and substantially inclosed thereby,

. binding means to hold the parts of said insulator in position, each of said domes having a substantially uniform thickness substantially proportional to its mean diameter to equa'bly apportion the condenser potential on said domes.

32. The compound insulator comprising a series of more than two petticoats and integral. imperforate domes, binding hold the parts of said insulator in position, each of said domes having an average thickness substantially proportional to'its mean diameter to Qquably apportion the condenser potential on said domes.

33. The compound insulator comprising a metallic body portion, a series of petticoats and attached imperforate domes nested within said body portion and protected and substantially inclosed thereby, binding means holding the parts of said compound insulator together,each of said domes having a substantially'uniform thickness substantially proportional to its mean diameter means to I to apportion the condenser potentials equably between the difi'erent domes and the inner petticoat integral with said inner dome. offering less resistance to the passage 'of- 34. The com ound lnsulator comprising.

a series of pettlcoats and attached imperforate domes, binding means holding the parts of said compound insulator together, each of said domes having a substantially uniform thickness substantially proportional to its mean diameter to apportion the condenser potentials equably between the dif-. ferent domes and the inner petticoats integral with said inner dome offering less resistance to the passage of electricity around it than the petticoat outside thereof to promote the self-protecting action of the insulating elements.

35. The compound insulator comprising a series of petticoats andattached imperforate domes, binding means holding the parts of said compound insulator together, each of said domes havin an average thickness substantially proportlonal to its mean diameter to apportion the condenser potentials equably between the different domes and the inner petticoat integral with said inner dome offering less resistance to the passage of electricity around it than the petticoat outside thereof to promote the self-protecting action of the insulating elements.

36. The compound insulator comprising a series of petticoats and attached imperforate domes, binding means holding the parts of said compound insulator together, each of said domes having an average thickness substantially proportional to its mean diameter to apportion the condenser poten tials equally between the different domes.

JOHN D. E. DUNCAN. Witnesses:

HARRY L. DUNCAN, JESSIE B. KAY. 

